Internet Explorer 8 predates the 'responsive' design era as well as HTML5 and CSS3. As a result, it's not easily made responsive. For example, we use Twitter Bootstrap, which doesn't work in IE8. We also use shadows on things which also doesn't work in IE (8 and 9). You'd have to replace all our bootstrap related stuff somehow and that isn't going to be easy.

If you know CSS, you may be able to make some elements more responsive. But the big question... why would any mobile device or computer that needs responsive design be using an outdated browser? Microsoft is even replacing IE with Safari for mobile devices.